In the glass industry today the most common glass container manufacturing machine is the Hartford type "I.S." machine. It is estimated that in the United States alone, there are over four thousand "I.S." machine sections in daily operation. The basic I.S. machine is described in U.S. Pat. Nos. 1,843,160; 1,911,119 and 2,289,046.
In a conventional Hartford I.S. type of glass bottle machine, the plurality of independent sections are operated in timed relationship to one another. Individual gobs of molten glass from an automatic feeding device are fed to the blank side of each of these sections in timed relationship to one another. Each section has one or more upwardly open blank molds for receiving the molten gob, or groups of gobs, and a baffle is adapted to move in and close the open end of the blank mold to permit the gob to be pressed or otherwise formed from below in order to form an inverted parison at the blank station. This inverted parison is swung over to the blow side of the section where it is placed in an upright orientation in a finishing or blow mold. A blow head decends onto the top of the finishing mold and the parison is blown into its final shape while the transfer mechanism returns with the neck ring mold to form another parison.
Today the lower cost bottle manufacturers are operating triple gob, narrow-neck, blow-and-blow equipment on 7-17 oz. single service beer and beverage bottles in order to obtain the economics of the increased production. A triple or quadruple gob, narrow-neck, press-and-blow operation would be much more economical because it would have the ability to produce more uniform distribution in the bottle, allowing production of lighter-weight ware.
The production rate per cavity in present day narrow-neck press-and-blow operations is not superior to the production rate of the narrow-neck, blow-and-blow operations, although the wide-mouth press-and-blow operation is a substantially higher speed operation than a wide-mouth blow-and-blow operation or a narrow-neck blow-and-blow operation at the same weight and capacity. The reason for this lack of speed in the narrow-neck press-and-blow operation is the necessity of running a "soft" parison. The soft parison allows the parison to "run" in the blow mold until it reaches the proper length to blow. This reduces the available blow mold time for expanding the parison and cooling the glass bottle.
Further, in producing a soft parison less heat is removed from the parison by the blank mold parts, leaving more of the total heat to be removed by the blow mold parts. This is another factor in the lower speed of production.
The primary objective of the present invention is to produce light weight glass bottles in a multiple cavity narrow-neck press-and-blow operation by providing a process which is more productive than current narrow-neck methods and capable of producing lighter weight containers with adequate strength.
Another objective of the present invention is to provide an improved method of making glass containers by creating a time overlap between the parison forming and inverting operation; an intermediate parison elongating operation; and the parison blowing operation, whereby the available reheat time for the parison is increased with no decrease in production output.
Present multiple gob blow-and-blow bottle manufacturing practice produces a parison the length of which is close to the height of the blow mold cavity so that blowing the parison in the blow mold can start shortly after the delivery of the parison to the blow mold. Such long parisons are more difficult to control in the transfer from the blank mold to the blow mold and, further, exhibit variations in the glass distribution which are minimized by the present invention.